docs: def show_environment(self, name=None):
          """Show environment ``$ tmux show-environment -t [session] <name>``.
  
          Return dict of environment variables for the session or the value of a
          specific variable if the name is specified.
  
          Parameters
          ----------
          name : str
              the environment variable name. such as 'PATH'.
  
          Returns
          -------
          str or dict
              environmental variables in dict, if no name, or str if name
              entered.
          """
          tmux_args = ['show-environment']
          if self._add_option:
              tmux_args += [self._add_option]
          if name:
              tmux_args += [name]
          vars = self.cmd(*tmux_args).stdout
          vars = [tuple(item.split('=', 1)) for item in vars]
          vars_dict = {}
          for t in vars:
              if len(t) == 2:
                  vars_dict[t[0]] = t[1]
              elif len(t) == 1:
                  vars_dict[t[0]] = True
              else:
                  raise ValueError('unexpected variable %s', t)
  
          if name:
              return vars_dict.get(name)
  
          return vars_dict